refactor(user): split user-machine into helpers and actors

Mirror the existing chat-module structure (chat-machine.helpers.ts +
chat-machine.actors.ts) for consistency across state-machine modules.

Split:
- user-machine.helpers.ts: pure data layer (no XState dep)
  - userStorage singleton
  - InitData interface
  - toView DTO → UserView mapper
  - readInitData (parallel getUser + getAvatarUrl)
- user-machine.actors.ts: async actor implementations (fromPromise)
  - userRepo / authRepo injection
  - userInitActor / userFetchActor / userLogoutActor
- user-machine.ts: only setup().createMachine() — keeps inline assign
  actions referencing context/event where they belong, imports actors
  (not helpers, per the layered convention).

No behaviour change — only file boundaries moved. Public API (exports of
UserState / UserEvent / initialState / userMachine / UserMachine) stays
identical so external imports are untouched.

src/stores/user/user-machine.helpers.ts

@@ -0,0 +1,105 @@
+/**
+ * User 状态机：纯函数 + 数据加载
+ *
+ * 从 `user-machine.ts` 抽出的"Helpers"段：
+ *   - InitData 形状
+ *   - `toView`：DTO → UserView 映射（纯函数）
+ *   - `readInitData`：从 UserStorage 读 user + avatarUrl（并行）
+ *   - `userStorage` 单例：被 helpers 和 actors 共用
+ *
+ * 设计目标：
+ *   - helpers 无 XState 依赖（可独立 import / 测试）
+ *   - actors 依赖 helpers（import）
+ *   - machine 依赖 actors（import）—— 不直接依赖 helpers
+ */
+
+import type { UserView } from "@/models/user/user";
+import { UserStorage } from "@/data/storage/user/user_storage";
+import { Result } from "@/utils/result";
+
+// ============================================================
+// Storage singleton
+// ============================================================
+/**
+ * UserStorage 单例 —— 被 helpers（readInitData）和 actors（userFetchActor / userLogoutActor）
+ * 共同使用。从 helpers 导出，避免在 actors 里重复 `UserStorage.getInstance()`。
+ */
+export const userStorage = UserStorage.getInstance();
+
+// ============================================================
+// InitData 形状
+// ============================================================
+/**
+ * `userInitActor` 的输出形状（user-machine.initializing.onDone 用）——
+ * 拆分 user 和 avatarUrl 是因为它们来自 UserStorage 两个独立接口。
+ */
+export interface InitData {
+  user: UserView | null;
+  avatarUrl: string | null;
+}
+
+// ============================================================
+// DTO → UserView 映射
+// ============================================================
+/**
+ * UserView DTO → UserView 视图模型（纯函数，可单测）
+ * - 与 chat 的 `localMessagesToUi` 同模式
+ * - 默认值收敛在此：undefined → "" / 0 / false，避免下游到处判空
+ */
+export function toView(u: {
+  id: string;
+  username: string;
+  email?: string;
+  avatarUrl?: string;
+  intimacy?: number;
+  dolBalance?: number;
+  relationshipStage?: string;
+  currentMood?: string;
+  isGuest?: boolean;
+  isVip?: boolean;
+  voiceMinutesRemaining?: number;
+  stripeCustomerId?: string | null;
+}): UserView {
+  return {
+    id: u.id,
+    username: u.username,
+    email: u.email ?? "",
+    avatarUrl: u.avatarUrl ?? "",
+    intimacy: u.intimacy ?? 0,
+    dolBalance: u.dolBalance ?? 0,
+    relationshipStage: u.relationshipStage ?? "",
+    currentMood: u.currentMood ?? "",
+    isGuest: u.isGuest ?? false,
+    isVip: u.isVip ?? false,
+    voiceMinutesRemaining: u.voiceMinutesRemaining ?? 0,
+    stripeCustomerId: u.stripeCustomerId ?? null,
+  };
+}
+
+// ============================================================
+// Init 数据加载（userInitActor 用）
+// ============================================================
+/**
+ * 并行读 user + avatarUrl（UserStorage 两个独立接口）。
+ * - 任意一个失败 / 无数据 → 对应字段返回 null，不抛错（与 chat 的
+ *   `readAndSyncHistory` "失败不卡 init" 一致的设计）
+ * - Result.isOk(_) && data 双重判空：Result 包装层 + 业务 null
+ */
+export async function readInitData(): Promise<InitData> {
+  const [userResult, avatarResult] = await Promise.all([
+    userStorage.getUser(),
+    userStorage.getAvatarUrl(),
+  ]);
+
+  let user: UserView | null = null;
+  if (Result.isOk(userResult) && userResult.data) {
+    user = toView(userResult.data);
+  }
+
+  let avatarUrl: string | null = null;
+  if (Result.isOk(avatarResult) && avatarResult.data && avatarResult.data.length > 0) {
+    avatarUrl = avatarResult.data;
+  }
+
+  return { user, avatarUrl };
+}